Centrifugal fan or pump.



.S. C. DAVIDSON.

GENTRIFUGAL FAN OR PUMP APPLICATION FILED NOV. 17, 1913'.

' Patenned Opt. 27, 1914.

- UNITED STATESPATENT OFFICE.

, CENTRIFUGAI; FAN OR- PUMP.

, 1,114,866, Specification f Letters Patent Patented Oct. 27, 1914.

I Applicationfiled November 17, 1913. Serial No. 801,447.

ToaZZ tehom ttm zy concern: ends of the blades, theterniinal portion of Be it known that I, IS iMUsL -GLELAND the casing which 1s disposed within the in- DAYlDSON, of slrocco Engineering lVo'i-ks, take chamber being curved outward toward. Belfast, Ireland, have invented certa1n new the 1 nor edges of the blades so as to etfec- 60 5 and useful lniprovements in or Relating to tivelyi solate the recirculatedair from the Centrifugal Fans or Pumps, of which the fresh air which passes through the intake follgwing i a ifi ti chamber to the. positive portion of the Thisiiivention refers to centrifugal fans blades. g Y or pumps of the incased type, and relates to The accompanying drawings show some 65 an improved construction of the inclosing Constructions embodying the present invencasing thereof. 7 tion.

In a previous British patent granted to igure l is across section of a single in me, No. 21,286 dated 23rd. October, 1901, I take'fan; Fig. 2 is a side elevation of Fig. have set forth a construction and arrangeig- 3 is a crosssection of a double in- 70 ment of fan and easing wherein the spiral take fan.

whirl of air, which leaves the positive'ends In the construction shown in Fig. 1 which of the blades, passes over as therein deshows the application to a single intake fan, scribed, to the negative ends of the blades, the cross sectional form of the inclosing easandis guided around said negative ends as ing a is such, that, after it springs substan- 75 go far as the plane of the intake end of the-fan tially radially Out d at a" rom the back wheel and thereat directed into the intake or positive end of the fan wheel 6 it then chamber of the fan wheel wherein it meets curves over the fan blades as at a to and and mixes with the current of fresh air beyond the plane of rotation of the negative flowing through the eye into the center of end at ofthe fan wheel. whereby the air be- 5 2'5 the fan Wheel. This patent is hereinafter ing discharged from the positive end 2) (if referred to as my first prior patent. the fan wheel whirls over, somewhat in- In a further British Patent No. H76, dicated by he arrows and along the inner granted to me, and dated 18th. January, surface of this curved interior of the casing 1912, I have described certain operative in what mightbe described as a cork-screwsophenomena whereby the air discharged like flow to and outwardly beyond the nega from what is referredto as the positive tive end of the fan wheel and by the furends of the fan blades, passes across, and rether extension of this curvature a inward enters the fan wheel centripetally throughand back through the intake opening'or eye the spaces or ports between the blades at as at a to within the plane of said negative 90 5 their negative ends. The central part of end of the wheel so that its terminal edge a the blades between the negative and posiforms a circle of loss diameter than that of tive ends being referred to as the neutral the inner edges of the blades and is located point. near to but not beyond the neutral part 0 According to the present invention I emof the inner edges of the blades whereby the 95 40 ploy a" casing which in section surrounds recirculating portion of the air thus guided,

but is spaced apart from the blades of a fan is directed axially along, or against the. inwheel so as to leave exposed to the intake ner edges of the blades in the direc Jn of chamber only the -positive portions of the the positive ends thereof. By this kuilStl'UC- blades whereby the portion of recirculating tion the portion of the recirculating air, 10

air which has passed over and inward which has passed over, and inward around around the negative ends of the blades is the negative ends of the blades, and is directed against the inner edges of the nega finally directed axially along or. against tive portions of the blades and is effectively their inner edges is effectively isolated by isolated from the fresh air entering through the part a within the plane of the negative 10;

Be the inlet opening or eye. 1? or example I end of the fan wheel from the current of may combine with a fan wheel of the kind fresh air entering the center'thereof through 9 having an intake chamber within the inner the most restricted part of the inlet opening,

, edge of the blades a casing spaced apart or eye, which in this construction, if formed from the periphery intake end, and inner by the inward and axial extension (4 of the edges of the fan wheel as to leave roonrfor casing to its terminal edge a and the curthe recirculation of air around the intake rents of recirculated and fresh alr are smoothly mixed together without turbulence along the inner edges 'of the'positive parts of the blades, whereas in my first prior patent, this isolation of the c'urrentsis not 5 maintained to within the plane of the intake end of the fan wheel. I

Th formation of the casing will be suitably modified in the case of a double intake fan and that portion of the casing which is coincident with the central plane of the fan wheel may be carried inward toward the periphery of the fan wheel or not as may be required. Fig. 3 shows a construction applied to a double intake fan Wheel the construction being a iluplication' of that shown in Fig. 1, the central part of the casing being carried inward at 0 to properly direct the currents discharged from the positive parts of the blades toward and around the negati e part in the manner herein set forth.

What I claim and desire to secure by Letters Patent is z- 1. A centrifugal fan having a wheel with blades wherein the axial length is greater than the radial depth, a peripheral casing therefor which is turned so as to pass around the inlet end of said Wheel and inside of the same being spaced therefrom and the edge of which at the intake end. is curved toward said wheel so far as to isolate the positve end of the blades from the recirculating current r and to isolate the negative end of the blades from the incomin fresh air.

,2. A cent-rlfuga fanhaving a wheel with blades wherein the length is greater than the radial depth, a peripheral casing therefor, an eye connected to said casing and providing therewith a recirculating a1r space around the periphery and intake end of the Wheel and then turned outwardly toward the inner edge of said blades whereby the recirculating air current is effectually isolated from the in oming fresh air and delivered on to the intake ends of the blades without being previously permitted to mix with the incoming fresh air.

8. A centrifugal fan having a wheel with blades wherein the axial length is greater than the radial depth, a peripheral casing therefor which extends around the intake ends of said blades and the end of which is turned inside of said Wheel and is then curred outwardly toward said blades so that its terminal edge expands adjacent to but not beyond the neutral part of said blades,

said casing paced apart from the periphery intake end l inside of said blades whereby the DOSltU'Q ends of said blades are isolated from the current ot an: recirculated around the negative ends thereof and the negative ends of said blades are isolated from the-11h coming fresh air.

in witness whereof. I have hereunto signed my name in the presence oftwo sub- 

